The investigators will study the cellular and molecular transport operations by which individual ions such as Na, K, Cl and H traverse single membranes of tubule cells. In addition, the mechanism(s) by which transepithelial fluid movement is coupled to that of solutes will be explored. Isolated tubules, renal cell cultures, single tubule cells, single cell membranes, renal membrane preparations as well as purified transport proteins will be used. Morphological, biochemical, cell biological and molecular biological techniques including morphometry, immunocytochemistry and molecular probes (antibodies to various membrane proteins) will complement the functional assessment of individual transport parameters (ion pumps, transporters and single channels). Core facilities will importantly support the group research effort and a wide range of collaborative studies. The research projects will evaluate fundamental properties of renal transport processes and deranged body fluid homeostasis. The results of our studies will have an impact on understanding renal disease (fluid and acid-base metabolism) and the rational treatment of fluid balance disorders.